Robert King was born in Pasadena on 6 June 1908, the elder of two sons of Arthur Scott King (1876-1957), a noted laboratory spectroscopist who was superintendent of the Physical Laboratory at Mount Wilson Observatory (MWO) from 1908 until 1943. Bob therefore came into contact with astronomers during visits to his father's laboratory and developed a natural appreciation for the activities and lifestyle at a major scientific research institution.
Bob attended Pomona College from 1926 to 1930 where he concentrated in physics and astronomy and decided to take up astronomy, a decision that greatly pleased his father. Partly through his father's contacts with Henry Norris Russell, Bob obtained a research assistantship in the astronomy department at Princeton University for the following year. After his first year at Princeton Bob married Helen Leonard, whom he had met at Pomona.
The summer after graduation Bob worked with his father in the Mount Wilson Physical Laboratory and obtained invaluable and unique practical laboratory experience. His analysis of the spark spectrum of ionized cerium resulted in his first scientific publication in 1932, and was the beginning of a long and fruitful collaboration between the two Kings. He did nearly all of his experimental research there, returning every summer while attending graduate school and between his three academic years as a physics instructor at MIT.
At Princeton Bob took astronomy courses but concentrated on physics, studying spectroscopy under A. G. Shenstone. Russell took a close interest in Bob's career, partly because he saw in Bob an opportunity to strengthen the bond between his Princeton group and experimental spectroscopy at Mount Wilson. Both Arthur King and Russell persuaded Bob to undertake a doctoral thesis on Zeeman effects in sunspot spectra, based upon high-quality data from the Mount Wilson 150-foot tower telescope which had never been fully analyzed. Bob applied new insights from recent advances in quantum mechanics, and was awarded the PhD in astronomy in 1933.
King obtained a National Research Council (NRC) postdoctoral fellowship for 1933-1935 to continue spectroscopic research at the Mount Wilson laboratory. There he began experimental measurements of f-values, or oscillator strengths, to obtain quantitative analyses of line intensities in stellar spectra. When King began experimental f-value determinations in 1933, reliable f-values were known for only a handful of lines, but these mainly were for resonance lines of elements of limited astrophysical significance. At Mount Wilson, Bob used the King furnace built and refined by his father for the initial determinations of relative f-values for several hundred lines of iron, titanium and vanadium which are abundant in solar-type spectra. In 1935 King accepted a three-year appointment as instructor in physics at MIT where he taught freshman physics. In collaboration with Donald Stockbarger of the MIT physics faculty, Bob began to design and construct a special closed-cell electric furnace that they would later use at Mount Wilson in the first attempts to measure absolute f-values for iron-group elements.
In 1938, King returned to the Mount Wilson laboratory as assistant physicist. Arthur King was approaching mandatory retirement age and Bob was the leading candidate to take over. In early 1942, with the nation at war, King joined the Caltech Rocket Project which was formed to develop small, solid-propellant rockets. He became the leader of the Fuse Group, consisting of about eight PhD scientists and engineers plus supporting draftsmen, machinists, and technicians. One of his group's early successes was an antisubmarine rocket fuse which entered combat in late 1942. King and his team received a Naval Ordnance Development Award in 1945 and a Presidential Certificate of Merit in 1948.
Bob King returned to Mount Wilson in January 1946, just as the first of several organizational changes prompted by the imminent completion of the 200-inch Hale telescope were taking place. Between resumption of war-suspended work on the 200-inch mirror in 1946 and the dedication at Palomar in 1948, a detailed agreement was worked out between Caltech and the Carnegie Institution for joint operation of the combined observatories to be known as the Mount Wilson and Palomar Observatories. This included a reorganized Division of Physics, Mathematics, Astronomy, and Electrical Engineering, and Caltech would henceforth offer graduate degrees in astronomy and astrophysics.
Creation of the combined Mount Wilson and Palomar Observatories was a major turning point in Bob King's career. Ira S. Bowen, who became director of MWO in 1946 and succeeded to the directorship of the combined observatories in 1948, called upon King to supervise Caltech doctoral students wishing to do spectroscopy. The first two of King's Ph.D. students began experimental work at the Santa Barbara Street laboratory in 1946, but King soon moved to the Caltech campus to take advantage of the large and well-equipped facilities there. Accordingly, on 30 June 1948, King became associate professor of physics at Caltech. Even so, the King furnace and large grating spectrographs at Santa Barbara Street continued to be used into the 1960s by King and several of his students for a number of research studies requiring these unique facilities.
Bob King spent the next 20 years as professor of physics at Caltech, attaining full professorial rank in 1952. At Caltech emphasis was on research and on supervision of graduate research theses. Bob kept a regular, but rather light, teaching load of graduate level optics and spectroscopy courses. He frequently served as the physics representative on astronomy PhD oral examination committees, in addition to many in physics. He supervised 13 Caltech doctorates, and continued research on the experimental determination of f-values for astrophysically important atomic spectra. As the years progressed, requirements for additional relative f-value studies leveled off and emphasis shifted to the considerably more difficult problem of the precision determination of absolute f-values for a few key lines of selected elements. In the mid 1950s, King's group inaugurated a series of absorption experiments based on atomic beam methods and eventually obtained excellent f-value results. During the 1950s and 1960s, King's Caltech group was one of about four leading centers worldwide conducting this type of experimental work.
In June 1968, at age 60, Bob took early retirement and moved to his ocean front home near Mendocino in northern California. The Kings enjoyed 20 years of quality retirement there playing golf and travelling. In 1988, at age 80, he suffered a stroke, and though he recovered somewhat he and his wife moved back to Pasadena to be near to their two daughters' families and to be closer to specialized medical care. Bob suffered declining health but remained alert, passing away peacefully in his sleep on 12 January 1995 at age 86. He is survived by Helen L. King, his wife of 64 years, two daughters, and three grandsons.
Robert King was highly regarded, especially by his students, who benefited greatly from his helpful advice and quiet guidance. He was a kind and modest gentleman, liked and respected by all who knew him. A March 1992 oral history is on file at the American Institute of Physics and was used in drafting this notice, as was a draft chapter from a biography of Henry Norris Russell by David DeVorkin. For a more detailed memorial and a bibliographical listing of King's work, contact the first author.
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